This invention relates to a calibration standard for an automated analyzer and, more particularly, it relates to a method for validating a replacement calibration standard for an analyzer.
Many analyzers, such as on-line automatic titration instruments, rely upon the use of on-line calibration standards. The response of the instrument to the calibration standard establishes a relationship known as a calibration curve. It is assumed that a given calibration standard is stable with time and the instrumental response to the standard is a true function of the analyzer's inherent behavior. Typically a calibration standard with a known concentration is available for routine on-line checking of the instrument's response to the standard. This can be done without human intervention by many analyzers as long as there is a sufficient quantity of the calibration standard.
At times, a calibration standard is consumed or a need otherwise arises to change the standard. When this happens, one or more new calibration standards are installed in the analyzer. The new calibration standards have known concentrations which, for example, are entered by human operators into the instrument. A fault can occur if the operator enters a calibration standard concentration incorrectly or if the standard itself has an incorrect concentration label. In the case where the on-line analyzer is used to provide information which is used directly in closed-loop control of production, an off-standard product could result from such a fault. Therefore, there is value in performing a validity check on calibration standards at the time when they are changed in an automatic analyzer.